We will continue studies of spindles in several directions. We will further characterize tubulin isolated from spindles and eggs of sea urchins and clams. Emphasis will be placed on calcium sensitivity, temperature dependence of this sensitivity, possible differences between unfertilized egg tubulin and spindle tubulin and possibility that tubulin from advanced larvae will be different from that of early states. We will intiate a study of the remnant left when spindles are deprived of actin, tubulin and membranes. This remnant still maintains spindle form. Studies will be under taken with scanning EM, high voltage EM, freeze-etching and freeze-substitution. In addition, we will attempt to dissect the structure with salts, enzymes, pH, etc. and correlate structure changes with removal of protein (or other components) identifiable with gel electrophoresis. We will continue studies of brain tubulin and its interaction with calmodulin utilizing purified reconstituted microtubules (tublin plus MAP-2, tubulin plus whole MAPs and tubulin plus tau), concentrating on possible differences between phosphorylated and non-phosphorylated components. We will continue studies of actomyosin gels from eggs which can be caused to contract in a unique manner: the gels will form on the container wall and will contract as a thin skin. Up to five such bags can form successively. This contractile skin may be a model for formation and contraction of the cleavage furrow. We will study it morphologically and with gel electrophoresis.